Method of producing composite metals



F b, 14, 1939, F. P. HUSTON ET AL 2,147,407

METHOD OF PRODUCING COMPOSITE METALS Filed Nov. '7, 1953 2 Sheets-Sheetl ffl1 5 8 INVENTOR FREDERICK P. HUSTON AND QEW WESLEY ATTORNEY Feb. 14,1939. F. P. HUSTON ET AL 2,147,407

METHOD OF PRODUCING COMPOSITE METALS Filed Nov. 7, 1933 2 Sheets-Sheet 2K N C N S N C INVENTOR FREDERlCK P. HUSTON ANDREW WESLEY b m M;

' ATTORilEY Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE FrederickP. Huston, Fanwood, and Andrew Wesley, Bayonne, N. J., assignors to TheInternational Nickel Company, Inc., New York, N. Y., a corporation ofDelaware Application November "I, 1933, Serial No. 696,946

22 Claims. I (Cl. 29-188) The present invention relates to cladded metalproducts containing chromium, and more particularly to composite metalsintegrally united and having a portion containing chromium and to amethod of producing suchcomposite metals.

Heretofore various methods have been proposed for the production ofcladded metal products, especially cladded metal products in which thebase metal or the cladding metal contains chromium. These prior methodsinvolved certain disadvantages and produced products having shortcomingsand/or defects. One of the worst disadvantages of prior cladded productscontaining chromium was that the cladded prodact could not be subjectedto certain stresses and certain operations without the cladding metaltearing from the base metal. For instance, the bending/and particularlythe twisting of prior cladded products containing chromium tore thecladding metal from the base metal. Although the art was struggling fora solution to the outstanding problem, none as far as we are aware, .waswholly successful and produced a completely satisfactory-product.

We have discovered a method of producing claddedmetal productscontaining chromium which is free from the disadvantages andshortcomings noted hereinabove and which is capable of producingsatisfactory,vsuccessfully and commercially acceptable compositeproducts.

It is an object of the present invention to provide a method which canbe carried into practice on an industrial scale to produce commercialarticles of manufacture economically and emciently.

It is another object of the invention to provide a cladded metal productcontaining chromium which can be bent and twisted without failing andwithout coming apart.

40. A further object of the invention is to provide a method in which abase metal or alloy can be integrally united to a cladding metal oralloy to produce a unitary article ,of manufacture containing chromium.I

45 It is also. within the contemplation of the invention to provide acladded metal product containing chromium which consists of a backing orbase metal which is relatively cheap or which has some desirableproperties not pos- 50 sessed by the surface coating and a claddingmetal or alloy which may be used to cover one or both' surfaces of thebase metal or alloy which contains chromium and which has superiorcorrosion and/ or heat resisting properties.

55 Other objects and advantages of the invention will become apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:-

Fig. 1 is a sectional view, somewhat diagrammatic of a pack of plates tobe bonded by the 5 present method;

Fig. 2'is a diagrammatic illustration, somewhat exaggerated, of aphotomicrograph of a section of the improved product showing the bondthereof; 10

Fig. 3 depicts a sectional view of a stack of plates encased in a metalcontainer for double cladding; and

Fig. 4 depicts a sectional view of a stack of plates encased in a metalcontainer for single 15 cladding.

Generally speaking, the present discovery contemplates the provision ofa film containing nickel or a nickel alloy to envelop or to coat themetal or alloy containing chromium. By incor- 2o porating the foregoingprovision in the process of producing cladded metal products, it ispossible to produce such products on an industrial scale readily anduniformly. The complete explanation of how the nickel fllm functions inthe 25 production of a satisfactory and successful composite productcontaining chromium has not been definitely established. As atheory, webelieve that the nickel or nickel alloy forms a bond having highphysical properties by partial inter- 30 diffusion into not only thechromium containing metal or alloy but also into the base metalespecially during the subsequent. hot working operations, and that thenickel film protects the surface of the chromium-containing alloy whenit is 35 heated. It is to be noted that the foregoing is merely advancedas a theoretical explanation of the success of the present method, butit is to be understood that if such explanation is found to beincorrect, it is to be disregarded. 40

Broadly stated, the invention contemplates the production of a claddedmetal product containing chromium which comprises a base metal or alloy,a cladding or coating metal or alloy containing chromium and anintermediate layer or film containing nickel or a nickel alloy which isadhesively united to the entire face of said chromium-containingcladding metal to form an integral unit. In carrying the invention intopractice, the surface of the chromium containing, metal or alloy isadhesively coated with a film of nickel or a nickel containing alloy andthe base metal having a clean surface is contacted firmly against thefilm of nickel and the two base metal and cladding metal are securedtogether in some appropriate manner as by clamping, weighting, welding,or the like. The composite product is then heated to a relatively hightemperature preferably in a reducing atmosphere.

made, hot working such as rolling, forging or the like may be employed.The heated composite product is then subjected to working operationssuch as forging, rolling or the like. After the bonding of the variouslayers has been accomplished not only hot working but also cold workingmay be employed. In the finished product thev base metal or alloy andthe cladding or coating metal or alloy are integrally united sothoroughly and effectively that the product can be stressed and deformedseverely without rupturing the bond between the base and the coating. Itis to be noted that the new composite product is particularly valuablewhere the product is to be used in structures which are subjected tosevere stresses or where the product is to be subjected to severefabricating operations. For instance, the improved product even in itsreduced or worked condition can be twisted into a helix or the likewithout the cladding metal tearing away from the base metal.

For the purpose of giving those skilled in the art a betterunderstanding of the invention the following specific example is givenfor the purpose of illustration.

A plate which is composed of chromium-nickel alloy and which is of aninch thick and-of any desired length and width iscleaned in anyappropriate manner, such as by sand blasting, pickling or the like; Inthis manner, a clean and scale-free surface is produced. To'this cleanedsurface a film of nickel or of a nickel alloy is 5 applied. Theapplication of the nickel flim may be effected, for instance, byelectroplating or by metal spraying or by any other suitable process.

In practice, it is preferred to apply the film of nickel or nickel alloyby means of electrodeposition. In the event that only one surface of aplate is to be cladded, it is preferred to place two equal sized platesback toback and secure them together by means of suitable clamps or thelike. The clamped plates which may be constituted of a chromiumcontaining metal or alloy such as a chromium nickel alloy, is immersedin anelectrolyte having a suitable composition for the electrodepositionof nickel or of a nickel alloy.

A film, coating or layer of nickel or nickel alloy is electrodepositedupon the cleaned surfaces of the plates arranged back to back. Theelectro deposition is conducted in any appropriate manner to yield adense, adherent deposit of nickel or nickel alloy. For instance, thechromium containing plates may be cleaned in the usual manner bytreating them as cathodes in an electrolytic alkaline cleaning bath.After' this operation the plates are rinsed in hot water and areimmersed in a solution of muriatic acid containing 5% by weight ofhydrochloric acid and heated to a temperature of about 150 F. They areheld in the acid solution for several minutes and are then transferreddirectly to a nickel plating bath where the coating of nickel iselectrodeposited. It is preferred to apply a coating of nickel having athickness of about 0.002" to about 0.005". of course, the thickness ofthe film or coating of nickel may vary considerably. Satisfactoryresults have been obtained from nickel coats having a thickness as lowas 0.001 of an inch and as thick as 0.005 of an inch. Of course, filmshaving thicknesses more than about 0.005" or less than 0.001" may beused.

In conducting the electrodeposltion of nickel any suitable nickelplating solution may be used. It is preferred to use the followingnickel plating solution and the following operating conditions:

Temperature 130 to 150 F.

Agitation Moderate air agitation Current density 50 amp. per sq. ft.Nickel sulphate 44 oz. per gallon Nickel chloride 2.2 oz. per gallonBoric acid 4.0 oz. per gallon Sodium sulphate (anhydrous) 13.8 oz. pergallon The nickel coated plates containing chromium are assembled in onecomposite pack or billet which may have any suitable arrangement. Asatisfactory assembly of the pack is diagrammatically illustrated inFig. l of the drawings.

Steel slabs I and 6 which have a thickness of about 3%" and of slightlygreater width and length than the nickel plated chromium containingplates have at least one surface cleaned in an appropriate manner suchas machining, sand blasting, grinding or the like. In this manner, a

' dry, grease-free, clean steel surface is obtained.

In setting up the stack or pack, it is preferred to lay steel slab lflat upon the floor with its clean surface facing upwardly. Upon steelslab l is placed the chromium containing plate 2 with the nickel coatedsurface 3 in contact with the clean surface of steel slab l A secondchromium containing plate 4 is laid upon the first chromium containingplate 2 with its nickel coated surface 5 exposed upwardly. Upon thenickel coated surface, a second steel slab 6 is placed with the cleansurface in contact with the nickel coated surface 5. In practice, it ispreferred to use welds l to secure the steel plates to thechromium-containing plates and to use welds 8 to secure thechromium-contalning plates together, as may be clearly seen in Fig. 1.It is to be noted, however,

that these welds should preferably be discontinuous and should bedisrupted at one or more points to provide vents in order to permit theescape of the expanding gases.

In the foregoing manner, a composite pack or billet is formed in whichthe clean surface of the steel slab and the nickel coated surface of thechromium containing plate are held together. The composite pack isheated to a temperature suitable for bonding. In the present instancewhere a steel slab is being cladded with a plate of an alloy of chromiumand nickel, a temperature of about 2000 F. to about 2300 F. ispreferred. The heating is effected preferably in a reducing atmosphere..When the entire pack has reached this temperature it is hot worked inan appropriate manner, as for example, hot rolled. It has been foundthat only a small amount of hot working is necessary to secure a goodbond between the steel slab and the nickel coated plate contalnlngchromium. In other instances, however, it has been found that a greatreduction in area can be effected, if desired. By hot rolling theaforesaid pack, it can be reduced to an appropriate over-all thickness.In the present instance it was reduced to about A of an inch.

After the pack has been worked or rolled to 'the desired extent theedges thereof canbe trimmed. In this manner, two cladded steel productsare produced each of which are about A of an inch in thickness. Thecladding is equal to about of the total thickness. Of course, the amount'of cladding can be varied depending upon the particular conditions. Formost practical purposes, the thickness of the cladded metal is fromflveto twenty per cent of the total thickness, depending on the thickness ofcladded metal needed to withstand the particular conditions ofcorrosion, abrasion, scaling, etc.

In Fig. 2 a diagrammatic illustration of a photomicrograph of theproduct produced in accordance with the foregoing method is depicted. Itwill be observed that the reference character 9 depicts a portion of thealloy of chromium nickel and reference character ill depicts a portionof the steel layer. Between the two layers 9 and I0 is' an in ermediatelayer ll constituting the nickel coat. Between the nickel layer and thesteel layer is a bond II. In the same way,-between layer 9 and H is abond l3. It was found that the product produced in accordance with thepresent method could be subjected to severe stresses and couldbesubjected to various fabricating operations. Not only could the productbe subjected to stresses and fabricating operations, but it could alsobe subjected to intense bending and twisting without the cladding metaltearing from the base plate of steel or without the bonds rupturing orfailing in any way. As a result of practical tests it has been foundthat the present product can be produced on an industrial scale and theproduct used commercially.

Under certain conditions, it may be desired heat a multiplicity ofcompost products at one time. For instance, if it is necessary to obtaina large production from a furnace in a short period of time, then it ispreferred to use the arrangement shown in Fig. 3. In this figure, thereference character K designates a metal container which completelyencloses the composite products to be bonded. In practice, it ispreferable to employ sheet metaLsuch as sheet steel, for container. Kbecause of its light weight, its ability to expand freely, its low cost,its adaptability for folding, welding, etc., and its easy cuttingproperties. Of course, the conventional containers or boxes of castmetal or alloy may be used, if desired.

It is tobe observed that chromium containing plates 2 and 4 do not weldto each other because their contacting surfaces have not been nickelcoated. Moreover, it is preferred to leave the surfaces of plates 2 and4 which are to be plated back to back in an uncleaned condition.Furthermore, the surfaces placed back to back can be coated with somerefrac ory material or the like which will eliminate all possibility ofplates 2 and 4 being stuck together mechanically or otherwise.

It is to be noted that the present invention provides a method ofproducing useful products.

' Thus, a composite metal may be produced which is cheaper than a solidalloy of the same composition as the cladding metal or alloy while atthesesses overall properties superiorto either the solid base metal oralloy or the solid coating or cladding metal or alloy. For example,stainless steel cladded copper would have the corrosion resistance ofstainless steel but would have a con- S. This stack of plates is hereintermed a set".

Asmany sets as desired may be stacked up. A sheet' of steel may then befolded around the stack and secured together as by welding or the like.In order to completely enclose the stack, end portions of sheet steelmay be welded to the open ends of the folded sheet. For the purpose ofpermitting the escape of gas from the welded container, a vent V may beprovided, preferably inthe top of the'container.

That stack of sets enclosed in the container is heated sufiiciently highto effect bonding of the nickel to the adjacent faces of the steelplates. Due to the fact that the stack is sealed in a container, theheating is practically independent of the furnace atmosphere. If theweight of the stack is heavy enough, the nickel will be stuck or unitedto the steel. Usually, it has been found sufiicient to press down on thetop of the stack. For instance, a heavy plate, weight or the like may beplaced on the top of the stack or the stack may be placed in a hydraulicpress. After this each unit set may be subjected to working operations,such as hot or cold rolling, forging, etc. When the units have beenworked or reduced to the desired extent, the cladded product is readyforfabricating operations to convert the same into'arficles of manufacture.

In the foregoing operations, it has been found that the bottom and topplates of chromiumcontaining material do not stick or bond to theadjacent walls of the enclosing container or stick together. It appearsthat a greenish scale is. formed on the chromium-containing plates whichprevents sticking or bonding. The composite units comprising a steelbase plate having a nickel coated cladding plate containing chromium oneach face of the steel. plate may be taken from the stack and handled ortreated separately. Under the influence of the conditions within thecontainer including heat, pressure and atmosphere, a diffusion bond iseifected between the nickel film or layer and the steel plate and be--tween the nickel and the chromium-containing plate. In this manner thetwo chromium plates and intermediate steel plate are united into anintegral double cladded unit. Of course, the integral double-claddedunits may be removed from the container by opening the same in anyapproa chromium-containing plate C is placed with the surface bearingchromium in contact with the surface of the container which may besteel. The

surface of the nickel film or layerN of the chro-' mium containing platefaces upwardly. Upon the nickel film or layer N, a steel plate 8 ismountoperations.

In the event that it is. desired, it is preferred to.insert a separatorbetween the top of the steel plate of any unit and the bottom of thechromium-containing plate of the next higher unit which makes contactwith the steel plate. It has been found that one or more uncleanedsheets of chromium-containing material function satisfactorily as aseparator. Of course, a layer of refractory material may likewise beused as a separator instead of the uncleaned sheets.

When the container is charged with singleclad units and is sealed, itmay be introduced into a furnace and heated to a temperature of atleastabout 1800 to 2000' F. and preferably 2300 I". for a period of at leastabout A to 2 hours. In other words, the container is subjected to heatand pressure sufiicient to insure the. bonding of the steel plate to thenickel film or layer and of the latter to the chromium-containing plateto form an integral unit. The container may then be opened and each unitmay be subiected to working, as rolling, forging and the like. Byapplying the desired amount of working, an appropriate reduction of areamay be eflected and the unit may be reduced to the desired size. Thefinal product is a single clad unit which has such a tenacious bond thata sample of about 5 inches long may be subjected to a twisting testwhich involves twisting the sample through 360 degrees and thenretwisting the sample to its original condition without the bondrupturing.

instances the chromium nickel alloy contains 14% of chromium, 6% of ironand 80% of nickel but other chromium-containing alloys may besubstituted therefor. Thus, for instance, any of the stainless steels,particularly those containing about 18% of chromium and about 8% ofnickel may be used and steel cladded products made with a clad ofstainless steel may be produced. Similarly, copper or other metals oralloys containing litle or no chromium can be substituted for steel toproduce a composite product having a base of copper or the like and acladding of a chromium-containing alloy.

It is also to be observed that the composite product canbe subjected tothe same fabricating operations as would be employed on a sheet or platecomposed of the base metal. The composite product with steel as the basemetal can be worked either hot or cold by spinning, pressing, drawing.flanking, bending, dishing, hammering, etc, and by the usual coldworking operations such as shearing, punching and drilling; joining byriveting, welding, lock-seaming, soldering, etc. It is preferred to coldwork the composite product cladon copper as a base, and it may besubjected to spinni ll, stamping, drawing, ressing. flansins. i s. t

Furthermore, it is to be noted that the addition of the bonded layer ofchromium containing alloy to mild steel, copper, etc. gives addedstrength to the base metal and enables the composite product to be morehighly stressed in tension, compression, or shear than would be safewith a plate or sheet of the solid base metal.

Moreover, the articles of manufacture which can be produced from thecomposite product include autoclaves, kettles, dye vats, soap boilingequipment, dairy tanks, truck tanks, beer fermenting and storage tanks,cooking utensils, and other equipment for the chemical, dairy, foodproducts, and allied fields, and the home.

It is to be noted that the present invention is not to be confused withproposed processes in which a separate sheet of ironis laid between asteel plate and a chome alloy plate. In this proposed process, it isnecessary to provide special means in order toproduce a bond for unionbetween the various parts. Thus, a deoxidizing agent such as an aluminumpowder or the like must be provided in order to dissipate oxygen gaseswhich'are present in the air spaces between the steel plate and theintermediate iron sheet and between the chrome alloy plate and the ironsheet. Furthermore, various fluxes have been proposed to facilitate thebonding of the various sheets and plates or the like. The presentinvention avoids the foregoing complicated process and provides aprocedure which produces reliably, consistently and uniformly coatedproducts with a tenacious bond throughout the inter-face of theconnecting surface of the plates or the like which are to be joinedtogether,

Although the invention has been described in conjunction with preferredembodiments, it is to be observed that modifications and variations maybe resorted to as one skilled in the art can readily understand. Thus,various modifications can be made in the individual steps of the novelprocess and the invention can be applied to the production of coatedwire, tubes, rods and the like by altering the shapes of the partsconstituting the composite pack or-billet.

Of course, equivalents of nickel or nickel alloys such as cobalt, ironand the like, may be em- It is to be further noted that in the presentployed provided the metal or alloy is adhesively united to the entiresurface of the chromiumcontaining plate or the like in order to form animpervious protective film. For adhesively uniting the nickel or nickelalloy or equivalent metal or alloy to the face of thechromium-containing plate, electroplating, spraying by the Schoopprocess, or the like may be utilized.

Claims directed to the novel composite metals disclosed herein arecontained in applicants copendingdivisional application, Serial No,246,946, filed December 21, 1938.

We claim:

1. The process of producing a cladded product which comprises treating amass of a chromiumcontaining alloy to produce a metallic surface bondthe iron to the nickel, and working the same under pressure to form aferrous product cladded with a chromium-containing alloy, said 2. Theprocess of producing a cladded product which comprises cleaning thesurface of a clad constituted of a chromium containing alloy to removefrom said surface films of a type tending to interfere with welding,said clad having such a chromium content as to make the alloysubstantially non-weldable by customary and conventional procedures,applying a substantially impervious nickel-containing film to a cleanedsurface of said chromium-containing clad while the surface issubstantially free from such films, cleaning a surface of a ferrousbase, placing the cleaned ferrous surface in contactwith the nickelsurface, securing said ferrous base to said chromium-containing clad,subjecting the same to a heat sufficient to bond the iron to the nickel,and

working the same under pressure to form a ferrous product cladded with achromium-containing clad, said cladded product being capable of beingsubjected to commercial fabricating operations and subjected to bendingand twisting tests without the chromium containing clad separating fromthe ferrous base.

3. The process of producing a cladded product which comprises thoroughlycleaning one surface of each of two chromium-containing plates havingsuch a chromium contentas to be substantially non-weldable by customaryand conventional procedures, depositing a substantially imperviousnickel-containing film on each cleaned surface while said surface issubstantially free from film forming ingredients of a type tending tointerfere with welding, interposing said two chromium-containing platesback to back with the nickel-coated faces, exposed between two steelplates, each of said steel plates having a clean surface to contact withsaid nickel film, partially sealing the edges of said plates together toform a composite unit, and subjecting said composite unit to heatsufficient to bond the nickel to the steel and the chromium-containingmaterial to the nickel, and working said plates under pressure to forman integral clad product, said integral clad product being capable ofbeing subjected to commercial fabricating operations and subjected tobending and twisting tests without the chromium-containing plateseparating from the steel plate.

4. The process of producing a cladded product which comprises thoroughlycleaning one surface of each of two chromium-containing plates havingsuch a chromium content as to be substantially non-weldable by customaryand conventional procedures, depositing a substantially each imperviousnickel-containing film on cleaned surface while said surface issubstantially free from film forming ingredients of a type tending tointerfere with welding, interposing a steel plate with clean surfacesbetween the nickel coated faces of said two chromium-containing underpressure to produce a double cladded product, said integral clad productbeing capable 'of being subjected to commercialfabricating operationsand subjected to bending twisting tests without the chromium-containingplate separating from the steel plate.

, 5. The process of producing a cladded product whichcomprisesthoroughly cleaning one surface of a chromium containing platehaving such a chromium content as to be substantially nonweldable byheat and pressure, depositing a substantially impervious nickel film onsaid cleaned surface while said surface is substantially free from filmforming ingredients of a type tending to interfere with welding, placinga steel plate having a clean surface incontact with said nickel film toform a single cladded set, stacking up a plurality of said sets,encasing said stack in a metal-container, subjecting said container toheat sufllcient to cause a bonding of said steel surface to said nickeland said chromium containing plate to said nickel to form an integralunit and working said integral unit under pressure to form a singlecladded product, said cladded product being capable of being subjectedto commercial fabricating operations and subjected to bending andtwisting tests without the chromium-containing plate separating from thesteel plate.

6. The process of producing a cladded product which comprises thoroughlycleaning a surface of a chromium-containing clad having sufficientchromium to interfere substantially with welding by heat and pressure,electrolytically applying a substantially impervious nickel-containingfilm to said cleaned surface of the chromium-containing clad to form anadhesive union throughout substantially the entire interface and toprotect the cleaned surface, cleaning a surface of a metallic base,placing the metallic base with the cleaned a chromium to interferesubstantially withwelding by heat and pressure, electrolyticallyapplying a substantially impervious nickel-containing filmto saidcleaned surface of the chromium-containing clad to form an adhesiveunion throughout substantially the entire interface and to protect thecleaned surface, cleaning a surface of a. metallic base, placing themetallic base with, the cleaned surface in contact with the nickelsurface, securing said base to said chromium-containing clad, subjectingthe same to a heat sufficient to bond the base to the nickel, andworking the same under pressure to form a base product cladded with achromium-containing clad, said cladded product being capable'of beingsubjected to commercial fabricating operations and subjected to bendingand'twisting tests without the chromium-containing clad separating fromthe metallic base. I

8. The process of producing a cladded product which comprises thoroughlycleaning one surface of each of two chromium-containing plates havingsuflicient chromium to interfere substantially with welding by heat andpressure, adhesively coating each cleaned surface with a substantiallyimpervious nickel-containing film while said surface issubstantially,free from film forming ingredients of a type tending tointerfere with welding, interposing said two chromium-containing productbeing capable of being subjected to commercial fabricating operationsand subjected to bending and twisting tests without thechromium-containing plate separating from the base I plate.

9. The process of producing a cladded product which comprises thoroughlycleaning one surface of each of two chromium-containing plates havingsuch a chromium content as to be substantially non-weldable by customaryand conven-- tional procedures, depositing a substantially imperviousnickel-containing film on each cleaned surface while said surface issubstantially free from film forming ingredients of a type tending tointerfere with welding, interposing a base plate,

with clean surfaces between said nickel-containing surfaces of saidchromium-containing plates to form a double cladded set, stacking aplurality of said sets upon each other to form a stack, enclosing saidstack of sets in a metal container, subjecting said container tosufilcient heat to bond the base to the nickel and thechromiumcontaining plate to the nickel to form integral units, and thensubjecting said units'to work to produce a double cladded product, saidcladded product being capable of being subjected to commercialfabricating operations and subjected to bending and twisting testswithout the chromium-containing plate separating from the base plate. 7

10.- The process of producing a cladded product which comprisesthoroughly cleaning one surface of a chromium-containing plate havingsufllcient chromium to interfere substantially with welding by heat andpressure, depositing a substantially impervious nickel film on saidcleaned surface while said surface is substan tially free from filmforming ingredients of a type tending to interfere with welding, placinga base plate having a clean surface in contact with said nickel film onthe chromium-containing plate to form a single cladded set, stacking upa plurality of said sets, encasing said stack in a metal container,subjecting said container to sufiicient heat to cause a bonding of saidbase surface to said nickel and said chromium-containing plate to saidnickel to form an integral unit and working said integral unit to form asingle cladded product, said cladded product being capable of beingsubjected to commercial fabricating operations and subjected to bendingand twisting tests without the chromium containing plate separating fromthe base plate.

11. The process of producing a cladded prod-' containing film to saidcleaned surface of the chromium-containing clad, while the cleanedsurface is substantially free from film forming ingredients of a typetending to interfere with welding, said chromium being present in suchcontent as to be substantially non-weldable by customary andconventional procedures, cleaning a surface of a copper-containing base,placing the cleaned copper suri'ace in contact with the nickel surface,subjecting the same to a heat sufiicient to bond the copper to thenickel, and working the same under pressure to form a copper productcladded with a chromium-containing clad, said cladded product beingcapable of .being subjected to commercial fabricating operations andsubjected to bending and twisting tests without the chromium-containingplate separating from the copper base.

12; The process of producing a cladded prodnot which comprisesthoroughly cleaning a surface of a--chromium-containing plate, applyinga substantially impervious nickel-containing film to the cleaned surfaceof said chromium-containing plate while said cleaned surface issubstantially free from film forming ingredients of a type tending tointerfere with welding, said chromium being present in such content asto be substantially non-weldable by customary and conventionalprocedures, cleaning a surface of a copper-containing plate, placing thecleaned copper surface in contact with the nickel surface, securing saidcopper plate to said chromiumcontaining plate by spot edge welding,subjecting the welded plates to sufilcient heat to bond the nickel tothe copper and the chromium-containing plate to the nickel, andsubjecting said plates to working under pressure to form a claddedproduct, said cladded'product being capable of being subjected tocommercial fabricating operations and subjected to bending and twistingtests without the chromium-containing plate separating from the copperplate.

13. The process of producing a cladded product which comprisesthoroughly cleaning one surface of each of two chromium-containingplates having such a chromium content as to be substantiallynon-weldable by customary and conventional procedures, electrodepositinga substantially impervious nickel-containing film on each cleanedsurface while said surface is sub stantially free from film formingingredients of a type tending to interfere with welding, interposingsaid two chromium-containing plates back to back with the nickel coatedfaces exposed between two copper plates, each of said copper plateshaving a clean surface to contact with said nickel film, sealing theedges of said plate together to form a composite unit, and subjectingsaid composite unit to sufficient heat to bond the nickel to the copperand the chromium-containing material to the nickel, and working saidplates under pressure to form an integral clad product, said claddedproduct being capable of being subjected to commercial fabricating operations and subjected to bending and twisting tests without thechromium-containing plate separating from the copper plate.

14. The process of producing a cladded product which comprisesthoroughly cleaning one surface of a chromium containing plate,depositing a substantially impervious nickel film on said cleanedsurface while said surface is substantially free from film formingingredients of a type tending to interfere with welding, said platehaving a chromium content such as to be substantially non-weldable bycustomary and con-' ventional procedures, placing a copper plate havinga clean surface in contact with said nickel film to form a singlecladded set, stacking up a plurality of said sets, encasing said stackin a metal-container, subjecting said container to sufficient heat tocause .a bonding of said copper surface to said nickel and saidchromium-containing material to said nickel to form an integral unit,and working said integral unit under pressure to form a single claddedproduct, said cladded product being capable of being subjected tocommercial fabricating operations and subjected to bending and twistingtests without the chromium-containing plate separating from the copperplate.

15. The process of producinga cladded product which comprises thoroughlycleaning a surface of chromium-containing clad having sufficientchromium to interfere substantially with welding by heat and pressure,applying an electrodeposited protective coating to said cleaned surfaceof said. chromium-containing clad to form an adhesive union throughoutsubstantially the entire interface and to protect the same, placing acleaned surface of a metallic base in contact with said protectivecoating to form a unit, subjecting said unit to a heat sufficient tobond the base to the protective coating and working the same underpressure to form a base product cladded with a chromium-containing clad,said cladded product being capable of being subjected 'to commercialfabricating operations and subjected to bending and twisting testswithout the chromium-containing clad separating from the metallic base.i

16. The process of producing a cladded product which comprisesthoroughly cleaning a surface of a chromium-containing plate havingsufficient chromium to interfere with welding by heat and pressure,applying an electrodeposited protective coating to said cleaned surfaceofsaid chromium-containing plate to forman adhesive union throughoutsubstantially the entire interface and to protect thesame, securing ametallic base plate to said chromium-containing plate by welding,subjecting the welded plates to heat sufficient to bond the protectivecoating to the metal of the base plate and also to bond thechromium-containing clad to the protective coating, and subjecting saidplates to working under pressure to form an integral cladded product,said cladded product being capable of being subjected to commercialfabricating operations and subjected to bending and twisting testswithout the chromium-containing plate separating from the metallic baseplate.

17. The process of producing a cladded product which comprisesthoroughly cleaning one surface of each of two chromium-containingplates having such a. chromium content as to be substantiallynon-weldable by customary and conventional procedures, applying aprotective film to the cleaned surface of each of saidchromiumcontaining plates, interposing said chromiumcontalning platesback to back with the protective films exposed between two base plates,each of said base plates having a clean surface to contact with saidprotective film, discontinuously securing the edges of said platestogether to form a composite unit, and subjecting said composite unit tosumcien't heat to bond the protective film to the base and thechromiumcontaining plate to the protective film, and working said platesunder pressure to form an integral clad product, said cladded productbeing capable of being subjected to commercial fabricating operationsand subjected to bending and twisting tests without thechromium-containing plate separating from the base plate.

18. The process of producing a cladded product which comprisesthoroughly cleaning one surface of each oftwo chromium-containing plateshaving such a chromium content asto be substantially non-weldable bycustomary and conventional procedures, applying a protective film to thecleaned surface of each of said chromiumcontaining plates, interposing abase plate having clean surfaces between the two chromium-containingplates with said clean surfaces in contact with said protective films toform a double cladded set, stacking a plurality of said sets upon eachother, enclosing said stack of sets in a metal container, subjectingsaid container to suflicient heat to bond the base and thechromium-containing plate to the protective film to form integral units,and then subjecting said units to work under pressure to produce adouble cladded product, said cladded product being capable of beingsubjected to commercial fabricating operations and subjected to bendingand twisting tests without the chromium-containing plate separating fromthe base plate.

19. The method of making composite metal articles composed of a facingmetal consisting of a chromium containing ferrous alloy havingsufiicient chromium to interfere substantially with welding by heat andpressure and a ferrous -of ferrous metal by the action of heat andpressure.

20. The method of welding high melting point chromium-containing metalshaving a strong tendency toward formation of film of a type tending tointerfere with welding, which comprises cleaning the surface of a bodyof such a metal to remove such film therefrom, building up over suchsurface while substantially free from such a film, a layer ofelectrolytically deposited nickel adapted to bond with such body ofmetal, causing such layer of nickel to diffuse with the body of metal,and uniting to such layer coated surface a ferrous body under conditionsadapted to produce a weld.

' 21. The method of welding ferrous bodies which comprises thoroughlycleaning the surface of a body of ferrous metal containing sufficientchromium to render the same substantially non-weldable to anotherferrous body by heat and pressure forming on the surface of saidchromiumcontaining body of ferrous metal while clean anelectro-deposited, closely adherent protective layer of nickel, andthereafter welding additional ferrous metal to such face by heat andpressure.

22. The method of uniting two not readily mutually weldable ferrousbodies one of which contains sufficient chromium to interferesubstantially with welding by heat and pressure which comprises cleaninga face of each such body to remove oxide, electro-depositlng over eachsuch face, while substantially oxide-free, a strongly adhering layer ofnickel, and thereafter welding together such nickel layers by heat andpressure.

ANDREW WESLEY." FREDERICK P. HUSTON.

